#323 - New Perspectives On Toxics -- Part 2: Male Reproductive System Is Harmed By Toxic Exposures,, 02-Feb-1993

The ancient Greeks observed that men heavily exposed to lead became
sterile. But this knowledge was not passed to the Romans, who stored
their drinking water and their wine in lead-lined containers. Romans
also added lead to some of their drinks as a sweetener. Based on
examination of lead in Roman bones, some historians conclude that the
Roman upper classes probably couldn't reproduce themselves,
contributing to the fall of Rome.[1]

Until very recently, scientists paid little attention to the effects of
environmental agents on human reproduction. The modern period began in
1941 when blindness, deafness and death were reported among the
offspring of pregnant women exposed to rubella (German measles). The
thalidomide catastrophe in 1954-1961 brought home the potential dangers
of chemicals, in this case a prescription drug. (See RHWN #322.) The
birth of nearly 20,000 defective children following a Rubella epidemic
in the early 1960s confirmed the association of environmental factors
and birth defects.[2]

As recently as the early 1970s, few state governments were maintaining
records of birth defects. In 1974 the federal government established
the first national register of birth defects, monitoring hospital
records that account for about 15% of all births.[3] Even today this
program monitors only birth defects observed in newborns, which
probably represent only about a sixth of the total defects that
actually occur because many defects do not become apparent for several
years.[2]

As of 1980, approximately 200,000 birth defects were estimated to have
occurred in the U.S., accounting for about 7 percent of all live
births. In addition, more than 560,000 infant deaths, spontaneous
abortions, stillbirths and miscarriages were recorded due to defective
fetal development.[2]

In 1990, the federal Centers for Disease Control (CDC) reported trends
in birth defects between 1979 and 1987 in the U.S. They looked at 38
specific defects and found that 29 of the 38 had increased, two had
decreased and 7 had remained stable.[3] The largest increases (29
percent and 20.2 percent) occurred in defects of the heart; no doubt
some of this increase is due to better detection methods. However,
there was also a 9.6 percent increase in eye defects and a 2.7 percent
increase in cleft lip, so it seems likely that real increases are
occurring.

As we reported last week, the traditional view of birth defects
highlights the role of women and disregards the role of men, even when
there is good evidence showing men exposed to toxic chemicals father
defective children. The traditional reason for ignoring such research
is that, until recently, there has been no satisfactory theory to
explain how male exposures could affect offspring, so a cause-and-
effect relationship could not be established. The argument was that
women are born with all the eggs they will ever have, so each egg can
be exposed to toxins over a long period. Men on the other hand, produce
new sperm constantly, so any individual sperm has only a brief
opportunity to be exposed to toxins.

Another reason for ignoring the effect of toxins on male reproduction
was the "macho sperm" theory, which said that only the fittest sperm
were hardy enough to go the distance necessary to fertilize an egg.[4]
According to this theory, defective sperm could never reach an egg to
fertilize it, so men couldn't be responsible for producing defective
children. Now research has shown that the female reproductive tract has
ways of moving sperms along whether they are healthy or defective.

Researchers used to believe that there was an effective barrier between
blood vessels and the tissues where sperm originates in the testes. It
is now known that the barrier is not effective against many chemicals.

Then of course there's a cultural bias, reaching back to the Salem
witch trials, to blame women for trouble. "You don't have to be Sigmund
Freud to figure out that there are cultural factors to say why we have
paid so much attention to the female and so little to the male," says
Dr. Devra Lee Davis, an epidemiologist with the National Research
Council.

Research during the past decade has shown that there are two basic ways
that chemicals can affect male reproduction.[5],6 Chemicals can
directly affect the testes, where sperm originates. The numbers of
sperm can be diminished, or some sperm can be damaged, or sperm may
even carry toxins directly into the egg. Alternatively, toxins can
attack the male nervous system, or endocrine system, affecting the flow
of hormones that act as messengers regulating the complex chemical
processes that must all work well for conception to occur.

No matter what the mechanism of damage may be, there is a growing body
of evidence showing that male exposure to toxins can produce defective
children. Here is a sampling:

** A nationwide study of 99,186 pregnancies in Finland showed an
increased likelihood of spontaneous abortion if the father was
occupationally exposed to rubber chemicals, solvents used in the
manufacture of rubber products, solvents used in oil refineries, or
ethylene oxide.[7]

** A study of 22,192 children born with birth defects in British
Columbia showed that paternal occupation as a fire fighter was related
to the occurrence of heart defects. Fire fighters are often heavily
exposed to carbon monoxide and to polycyclic aromatic hydrocarbons
(PAHs)--the nasty chemicals in smoke and soot.[8]

** A study of paternal occupation among 149 patients with Wilm's tumor
(a childhood cancer of the kidney) showed that a significantly greater
number of the fathers were exposed to lead on the job, compared to
fathers of a control group of children without the disease.[9]

** A study of 6000 men in Finland showed that paternal exposure to
organic solvents nearly tripled the likelihood of spontaneous abortion
as a pregnancy outcome, compared to controls not exposed to organic
solvents. Painters, wood workers (for example, carpenters in the
construction, furniture industry and the boat industry) were found to
be at risk. The solvent toluene stood out as a particularly bad actor
in his study.[10]

** A study of anesthetists in the West Midlands region of England (half
men, half women) showed that, during a 20-year period, 9.3% of their
children were born with defects, and 31% of the anesthetists reported
having trouble begetting children. Furthermore nearly all the children
were born underweight. The gender of the anesthetists did not affect
the likelihood of problems in their children, but female children seems
to suffer greater birth defects.[11]

** A recent review of several studies of paternal occupational
exposures in relation to childhood cancer in the offspring showed
consistently that work in hydrocarbon-related occupations (the
petroleum and chemical industries), especially exposure to paint, is
associated with brain cancer. Male exposure to paint is also linked to
leukemias in offspring.[12]

What does all this evidence mean? It means neither men NOR women can be
safely exposed to toxic chemicals. Instead of banning women from the
workplace, the workplace should be cleaned up.